B1 - cell structure and transport

Question 1

how many nanometers are in a meter

Answer 1

1 x 10-9

Question 2

advantages of a light microscope

Answer 2

Relatively cheap, can be used almost anywhere, can magnify live specimens

Question 3

advantages of an electron microscope

Answer 3

high magnification (x2000000), high resolution (0.2nm), can see subcellular structures

Question 4

disadvantages of light microscope

Answer 4

lower magnification (x2000) and lower resolution (200nm)

Question 5

disadvantages of electron microscope

Answer 5

large, very expensive, have to be kept in specific conditions (temperature, pressure, humidity)

Question 6

how do you calculate magnification

Answer 6

size of image/size of real object

Question 7

subcellular structures in animal cells and their functions

Answer 7

nucleus - controls activities of the cell
cytoplasm - where chemical reactions take place
cell membrane - controls passage of substances into cell (like urea, hormones, glucose and mineral ions)
mitochondria - site of aerobic respiration
ribosomes - site of protein synthesis

Question 8

extra subcellular structures in (most) plants and their functions

Answer 8

cell wall - strengthens + supports the cell
chloroplasts - contain chlorophyll for photosynthesis
permanent vacuole - keeps the cell rigid

Question 9

give an example of a eukaryotic cell

Answer 9

plant cells
animal cells

Question 10

give an example of a prokaryotic cell

Answer 10

bacteria (single called organisms)

Question 11

what is the difference between prokaryotic and eukaryotic cells

Answer 11

prokaryotic - genetic material is not enclosed in a nucleus but in a single loops of DNA and rings called plasmids
eukaryotic - DNA enclosed in a nucleus

Question 12

what is an order of magnitude

Answer 12

when something x10 bigger than another

Question 13

adaptations of a nerve cell

Answer 13

many dendrites - make connections to other cells
long axon - carries nerve impulses
synapses - pass impulses to another cell (also contain many mitochondria to provide energy for production of transmitter chemicals)

Question 14

adaptations of muscle cells

Answer 14

special proteins - slide over each other making the fibres contract
many mitochondria - transfer necessary energy for chemical reactions
store glycogen - can be broken down and used in cellular respiration

Question 15

adaptations of sperm cells

Answer 15

long tail - whips from side to side to help sperm move
full of mitochondria - provides energy needed for the tail to move
acrosome - stores digestive enzymes for breaking down outer layer of egg
large nucleus - contains all the genetic material to be passed on

Question 16

adaptations of root hair cells

Answer 16

large surface area - allows water to easily move into cell
large permanent vacuole - speeds up movement of water by osmosis
many mitochondria - provides energy needed for active transport of mineral ions

Question 17

adaptions of photosynthetic cells

Answer 17

chloroplasts - contain chlorophyll to trap light needed for photosynthesis
placed in continuous layers in leaves and outer layers of stem - absorb as much light as possible
large permanent vacuole - keep cell rigid, help support stem, keep leaf spread out

Question 18

adaptations of xylem cells

Answer 18

dead (due to lignin building up in spirals in cell walls) - form long hollow tubes that allow water and mineral ions to move through them
spirals and rings of lignin - make them very strong to withstand pressure of water moving up plant, support the plant stem

Question 19

adaptations of phloem cells

Answer 19

sieve plates - allows water carrying dissolved food to move freely up and down the tubes
companion cells - help keep them alive, mitochondria in companion cells transfer energy needed to move dissolved food up and down plant

Question 20

define diffusion

Answer 20

the spreading out of particles of a gas or of any solute in a solution from an area of high concentration to low concentration down a concentration gradient

Question 21

how do you figure out net movement

Answer 21

net movement = particles moving in - particles moving out

Question 22

greater difference in concentration would mean…

Answer 22

…a faster rate of diffusion

Question 23

how is diffusion used by oxygen in the lungs

Answer 23

oxygen needed for respiration passes from air in your lungs into red blood cells through cell membranes in alveoli by diffusion

Question 24

adaptations for diffusion

Answer 24

higher surface area - e.g. villi in the small intensine

Question 25

which substances move in and out of cells by diffusion

Answer 25

glucose (dissolved), urea (dissolved), oxygen (gas), carbon dioxide (gas)

Question 26

define osmosis

Answer 26

the movement of water from a dilute solution (high concentration of water) to a concentrated solution (low concentration of water) through a partially permeable membrane

Question 27

define isotonic

Answer 27

when the concentration of solutes in the solution outside the cell is the same as the concentration inside the cell

Question 28

define hypERtonic

Answer 28

when the concentration of solutes outside the cell is higher than the concentration inside the cell

Question 29

define hypOtonic

Answer 29

when the concentration of solutes in the solution outside the cell is lower than the concentration inside the cell

Question 30

what can happen if the concentration outside an animal cell changes dramatically

Answer 30

the cell may burst (hypotonic) or shrivel (hypertonic)

Question 31

what is turgor

Answer 31

when no more water can physically enter a plant cell

Question 32

why do plants always need their surrounding fluid to be hypotonic

Answer 32

keeps water moving by osmosis in the right direction and the cells are turgid

Question 33

what happens when the solution surrounding a plant cell becomes hypertonic

Answer 33

water leaves the cell by osmosis, becoming flaccid, no pressure on cell walls, plant wilts due to no turgor to support plant issues

Question 34

what happens when more water leaves the cell

Answer 34

the vacuole and cytoplasm shrink, cell membrane pulls away from cell wall (plasmolysis)

Question 35

define active transport

Answer 35

active transport is the movement of substances into a cell against a concentration (from low to high) across a partially permeable membrane

Question 36

why is active transport important (plants)

Answer 36

mineral ions in the soil (like nitrate ions) are found in very dilute solutions so need active transport to be moved into the cell

Question 37

why is active transport important (animals)

Answer 37

glucose is needed for cell respiration, sometimes concentration of glucose in blood is higher than concentration in gut, active transport must be used to move glucose from gut to blood

Question 38

adaptations for exchanging materials

Answer 38

large surface area
thin membrane (provides short diffusion path)
(in animals) efficient blood supply moves diffusing substances away from exchange surfaces to keep steep concentration gradient
(in animals) being ventilated makes gas exchange more efficient by keeping steep concentration gradient

Question 39

examples of adaptations for exchange in animals

Answer 39

alveoli in lungs
villi in small intestine
gills in fish

Question 40

examples of adaptations for exchange in plants

Answer 40

plant roots - large surface area (even bigger from root hair cells) to make uptake of water + mineral ions more efficient, water constantly moves away from roots in transpiration stream keeping steed concentration gradient
leaves - flat thin leaves, presence of air spaces in leaf tissues, stomata all provide big surface area